Edda is a term that applies to two written collections of Old Norse mythology known as The Poetic Edda and The Prose Edda. Both were presumed to be written in Iceland around the 13th century. Most popular Norse mythology is based on these works.
There are a few theories about where the word Edda came from. Among them are that it means word "great-grandmother" or that it means "the book of Oddi" which was an educational center of the time. The two most accepted theories are that is is derived from the Norse word for "poetry" or that is is a combination of the Latin edo meaning poetry, and the Icelandic kredda meaning superstition.
The Prose Edda, or The Younger Edda, is a historical Icelandic document of great importance. It is both a book of poetry and a sort of instruction manual, or treatise, on poetry. It was originally written down in approximately 1220 by Snorri Sturluson (1178-1241) and is therefore also called the Snorri Edda. The most important surviving manuscript dated approximately 1300 is known as the Upsala Codex.
It contains three separate sections: The Gylfaginning or "Gylfi's Deception," the Skáldskaparmál or "Diction of Poetry", and the Háttatal. Gylfaginning tells stories of creation and destruction by the gods and shares conversations between several of them. Skáldskaparmál has stories of mythology between collections of famous Norse poetic paraphrases and synonyms. Finally, the Háttatal contained 102 strophes, or sections of lyrical poems. Each of these is composed in a different meter and is followed by commentary from an unknown source.
The Poetic Edda is also sometimes called The Elder Edda. It is a collection of poems or songs that include many classic tales of Norse mythology. Gods like Odin and Thor are discussed as well as famous heroes and heroines like Brynhildr and Gunnar. The 29 most important are included in the medieval Codex Regius.
The Codex Regius was discovered in 1634 by Bishop Brynjólf Sveinsson. It was unknown where it came from or who wrote it. Since many of the poems were discussed by Snorri in The Younger Edda, the Bishop erroneously called it Edda. He also surmised, incorrectly, that the writer and priest Saemund had written it.
It has since been assumed that the Codex Regius is written in the oral tradition, although there is no certainty as to the author or age. Scholars presume that those works of The Elder Edda were written between the 9th and 13th centuries and are from Norwegian ancestry, whether it be from Norway itself or from its settlements in Iceland. Because of the confusion in authorship between these two texts, the term Edda has come to be a term used to describe any of these poetic mythologies, although it only technically applies to the Snorri Edda.